For many years, since the development of outdoor grilling appliances in the nineteen forties and fifties, there has been a desire for an effective electrically powered outdoor cooking appliance. It has long been believed that such a device might be made more convenient and easier to use, e.g., without requiring special fuel like a charcoal or propane. In recent years, the growing availability of electrical energy from renewable or otherwise environmentally friendly resources has added further impetus for the use of such electrical appliances.
The current electrical outdoor grilling appliance art includes two types of products. In the first type, an electrical resistance heating element is embedded in a cooking grate. As the current heats the element, the element transfers heat by conduction to the grate, which is usually made of a conductive material such as aluminum. The grate, in turn, heats the food by conduction. Typically, slots are provided in the grate for the drainage of grease. By alternating the contact areas and the open slots, the grill can produce, under favorable circumstances, a pattern of “sear” marks, which are desirable when grilling.
In the second type of product, a radiant heating element is suspended below an open wire-type cooking grate and surrounded by some type of insulating material. Food is cooked by radiant heat through the open grate and by some conduction from the cooking grate, which is heated by a radiant element. The conductive heat from the grate can produce, under favorable circumstances, the pattern of “sear” marks desired for grilling. This type of grill is generally described in U.S. Pat. No. 6,104,004.
The first type of grill suffers from the problem that the temperature of the heated cooking surface must be held below the ignition point of grease or fire will occur at the point of cooking. However, the required low temperature will not sufficiently vaporize grease to produce smoke that normally flavors the meat when grilling. Furthermore, the required low temperature allows accumulated grease to gather on the surface of the cooking grate around the food despite the provision of grease drainage features. This accumulated grease further reduces cooking effectiveness by acting as a liquid coolant for the cooking surface.
In the second type of grill, good cooking performance can only be achieved by cooking with the lid closed as much as possible since the design and cooking performance of these grills depend on the establishment of a large radiant cavity below and above the food that is supported on the grate, as shown in U.S. Pat. No. 6,104,004. If the lid is opened, the cavity is not only split into two open halves, but most of the radiant energy generated by the heating element is lost to the atmosphere with little effective retention by the food and the open wire-type cooking grate.
Both types of grills also suffer from a lack of power density. This condition is driven by wattage limitations of standard US residential electrical systems. An absolute upper limit of 1800 watts set by a 120 volt current limited by a 15 amp circuit breaker produces a thermal energy equivalent of 6,147 BTU/hr for an entire cooking surface. In the case of a 200 square inch cooking surface, a maximum power density of 30.7 BTU/hr/in2 results. This power density is very much lower than the common 100 BTU/hr/in2 maximum of a conventional gas grill and is still much lower than the 60 to 80 BTU/hr/in2 typical of some new gas infrared cooking systems. As a result, in less than ideal conditions, such as a cold windy day, the electrical cooking appliance may not produce adequate cooking results.